The present invention is directed to a strand element for an optical cable which element consists of several light waveguides for the transmission of optical signals or light waves which are received in a protective casing that surrounds the fibers and has an interior diameter which is larger than the exterior diameter of a hypothetical cylinder surrounding the fibers.
A structural element such as a strand element which has light waveguides such as fibers disposed in an outer protective casing with a clearance between the fibers and casing are known and an example is disclosed in German O.S. No. 25 28 991. Since the light waveguide fibers in this type of the construction can move relatively independent of the protective sheath, or casing, the light waveguide fibers are subjected to only low mechanical stresses during the bending of the strand element. However, this property is strictly only present for fibers which are located loosely in a tubular protective sheath. If on the other hand, several fibers are housed in a stretched form in the protective sheath, then bending will cause a mutual shifting of the fibers to occur and this mutual shifting can lead to undesireable mechanical stressing of the fibers.
In practical matters, there exists a need for a cable which has a rather large number of light waveguide fibers in a single housing and the mechanical stress for each fiber which is housed in this cable must be as low as possible. It has been suggested such as disclosed in German O.S. No. 25 28 991 that one can fulfill this demand by positioning each fiber loosely in a tubular protective sheath and to combine the so called hollow sheaths or elements according to known rules of engineering of telecommunication cables into a desireable cable structure. The combining of several light waveguides in one cable is also disclosed in German A.S. No. 26 28 069. In this reference, each of the fibers or communication cores is arranged in the center of the cable, each glass fiber possesses a rigidly applied sheath or coating and several such elements are housed loose and unstranded in a double layer protective casing. A suitable outer sheath or jacket is located over this casing. In general this cable construction is only suited for a limited number of communication elements or cores.